Last modified: December 2023

AHELP for CIAO 4.16 Sherpa


Context: models


The XSPEC grbjet model: Two-phase Comptonization model of soft thermal seed photons for GRB prompt emission



The xsgrbjet model is an additive model component.


The model is described at [1] .


>>> create_model_component("xsgrbjet", "mdl")
>>> print(mdl)

Create a component of the xsgrbjet model and display its default parameters. The output is:

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.thobs    frozen            5            0           30           
   mdl.thjet    frozen           10            2           20           
   mdl.gamma    thawed          200            1          500           
   mdl.r12      frozen            1          0.1          100           
   mdl.p1       thawed            0           -2            1           
   mdl.p2       thawed          1.5          1.1           10           
   mdl.E0       thawed            1          0.1         1000        keV    frozen          0.2         0.01          1.5           
   mdl.index_pl frozen          0.8            0          1.5           
   mdl.ecut     frozen           20          0.1         1000        keV
   mdl.ktbb     frozen            1          0.1         1000        keV
   mdl.model    frozen            1 -3.40282e+38  3.40282e+38           
   mdl.redshift frozen            2        0.001           10           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
thobs The observing viewing angle in degrees.
thjet The jet half-opening angle in degrees.
gamma The jet gamma Lorentz factor.
r12 The jet radius in 10^12 cm.
p1 The low-energy index of the coming frame broken powerlaw spectrum.
p2 The high-energy index of the coming frame broken powerlaw spectrum.
E0 The break energy in keV.
delta The smoothness of the transition between the two powerlaws.
index_pl The energy index of the comoving-frame cutoff powerlaw spectrum.
ecut The cut-off energy in keV.
ktbb The comoving frame blackbody temperature in keV.
model The comoving frame emissivity law: 1 is broken powerlaw, 2 is cutoff powerlaw, and 3 is blackbody.
redshift The source redshift.
norm The normalization of the model: see [1] for an explanation of the units.


XSPEC version

CIAO 4.16 comes with support for version 12.13.1e of the XSPEC models. This can be checked with the following:

% python -c 'from sherpa.astro import xspec;


See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also

xsgrbcomp, xsgrbm